Why ser and ir are so irregular

The purpose of this post is to share two of my favorite slides from the PowerPoint I prepared for my recent talk at the NECTFL conference. The slides summarize the history of the two most irregular Spanish verbs, ser ‘to be’ and ir ‘to go’. It turns out that each of these verbs is a historical merger of three distinct verbs. Ser merged the Latin verbs sedere ‘to sit’ and esse ‘to be’, which itself combined Proto-Indo-European verbs meaning ‘to be’ and ‘to become’. Ir merged the Latin verbs ire ‘to go’, vadere ‘to go, walk’ (a cognate of English ‘to wade’), and esse ‘to be’. As you can see from the slides, each root is responsible for a subset of each verb’s modern forms.


The history of “ser” (‘to be’). The asterisks indicate reconstructed (hypothesized) Proto-Indo-European roots.


The history of “ir” (‘to go’). My favorite detail here is that the singular command ‘ve’ and the plural command ‘id’ come from different Latin roots.

This type of historical process, in which one verb does a “hostile takeover” of part of another verb’s conjugation, is common enough to have its own name: suppletion. You can see suppletion in the English verb ‘to go’, whose past tense form went comes from the semantically related verb ‘to wend’. The various cases of suppletion in the histories of ser and ir are likewise plausible:

  • for sedereesse: ‘to sit’ is connected to ‘to be’ because it expresses location
  • for *hes*buh: ‘be’ and ‘become’ are obviously related
  • for irevadere: ‘walking’ is a kind of ‘going’
  • for ireesse: if you ‘are’ somewhere, it follows that you ‘went’ there. For example, you can say “I’ve never been to Barcelona” instead of “I’ve never gone to Barcelona”.

I will have to save these charts for the second edition of my book!

9 thoughts on “Why ser and ir are so irregular

  1. Nicolás

    Very good post. Just yesterday I was asking some professor if “eres” derived from the future tense “eris” in order to be different from “es”.

  2. Tk

    Just learning Spanish and was wondering about this, especially ir with it’s crazy irregularities (yendo? really?). Funny that someone has written an article about the exact subject, and relatively recently. Thanks for providing the breakdown.

    Also good to hear that these are two the the most irregular verbs in Spanish. I was beginning to worry the whole language was going to be like this.

    1. jhochberg Post author

      I’m glad you liked the post. I wished I had done this analysis before publishing my book. If there is a second edition I will add it as one of the 101 questions, which means I’ll be able to get rid of question #56, “How do you write Spanish on a computer”, which I’ve always thought was a bit of a stretch. You may also be interested on my post “The most frequent Spanish verbs are irregular.”

    2. Ramin Rouchi

      To answer your pondering….yendo can also be written as “iendo”. They are pronounced the same way albeit the first syllable of iendo is a bit longer and elaborated. Or yo..from Latin “ego”. The g softened until lost. In Italian it is spelled “io”.

  3. Alleyne

    Thank you for this! I was a little surprised when my Spanish etymology dictionary had nothing to say about this. I’m glad I glad persevered and found this article. I’m wondering what your source(s) are.

    1. jhochberg Post author

      Most of what I know about the history of Spanish comes from Ralph Penny’s book, “A history of the Spanish language.” I strongly recommend it although it is fairly dense reading. So for this post, for example, I read and extracted the relevant bits that had to do with these verbs, restructured the information, and put it down in a form that I thought would be most accessible.

      I am more of a popularizer and explainer than an original researcher.


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